钎焊温度对GH4169/1Cr18Ni9Ti接头组织和性能影响研究

采用BNi82CrSiB镍基钎料真空钎焊GH4169/1Cr18Ni9Ti母材,通过光学显微镜、能谱仪、显微硬度计、拉伸试验机等研究了钎焊温度对钎缝的显微组织、显微硬度、力学性能的影响。结果表明:在1 060~1 100℃范围内,接头的钎缝主要由镍基固溶体组成,钎缝中未出现金属间化合物相,钎焊温度的变化对接头的钎缝组织无明显影响。断口分析结果表明:接头断裂均为韧性断裂,断裂区域均处于靠近1Cr18Ni9Ti母材的扩散区中。     

铝合金/不锈钢高频感应钎焊接头结构与性能研究

采用自炼的Al-Si-Cu-RE钎料进行高频感应钎焊,实现了LF21铝合金与1Cr18Ni9Ti不锈钢的连接,利用电子万能试验机进行了钎焊接头剪切试验,利用SEM,EDS等手段对钎焊接头的微观组织进行研究和分析.微观结构分析表明,钎焊接头的显微组织由α(Al)-θ (CuAl2)共晶组成,高频感应快速加热避免了钎缝中Fe-Al金属间化合物的生成,且由于钎料中添加了RE元素,CuAl2相为均匀分布的枝状晶,Si相经变质处理细小分散;Al-Si-Cu-RE钎料与LF21铝合金反应良好,界面过渡均匀,钎缝与1Cr18Ni9Ti不锈钢之间有明显的分界,剪切试验表明接头抗剪强度达95 MPa.     

新型含钯镍基钎料钎焊不锈钢接头的性能分析

对新型Ni-Pd-Ag-Cr-Si钎料钎焊1Cr18Ni9Ti不锈钢的接头性能进行了分析。结果表明,新型Ni-Pd-Ag-Cr-Si钎料对1Cr18Ni9Ti不锈钢有良好的润湿性;钎焊接头中,紧靠钎缝与母材界面的是与该界面平行的长条形齿状镍钯基固溶体致密组织。这种固溶体具有较高的强度和塑性,钎缝宽度为170μm时,钎缝仍具有较高的剪切强度,利于保证钎焊不锈钢产品质量不发生重大变化。     

采用改进BNi-7钎料钎焊316L不锈钢

采用改进BNi-7钎料钎焊316L不锈钢,钎缝间隙为100μm,研究了Cu粉添加量、钎焊温度对接头组织及力学性能的影响。结果显示,采用BNi-7+x%Cu进行连接时,接头主要由不锈钢/钎料界面的Ni(Fe,Cr,Cu)固溶体和钎缝中心的Ni(Fe,Cr,Cu)-CrNiP共晶组织和Ni3P-Ni(Fe,Cr,Cu)共晶组织组成。钎缝中心Ni(Fe,Cr,Cu)-CrNiP共晶组织中分布的Ni(Fe,Cr,Cu)韧性相使脆性磷化物弥散分布;随着Cu添加量和钎焊温度的增加,钎缝中心的脆性化合物含量降低。当钎焊温度为980℃,Cu添加量为9%时,接头的抗剪强度最大为118 MPa。     

Ni-Mn-Si-Cu-B-Ce钎料钎焊性能的研究

为了满足在990~1010℃温度下钎焊不锈钢的需要,研究了一种Ni-Mn-Si-Cu-B-Ce钎料。对钎料的熔化特性和润湿性、接头组织以及钎焊搭接接头的剪切强度进行了研究。结果表明:微量元素B、Ce元素可使BNi66MnSiCu钎料的熔化温度显著降低,从而满足在990~1010℃温度下钎焊不锈钢,加入微量元素B、Ce元素后使钎料对1Cr18Ni9Ti不锈钢的润湿性影响较小,但钎料的剪切强度提高约133倍,利用Ni-Mn-Si-Cu-B-Ce钎料在钎焊1Cr18Ni9Ti不锈钢后,发生了互扩散效应,钎料与母材之间形成了牢固的扩散层;在Ni-Mn-Si-Cu-B-Ce钎料显微组织中,主要存在Ni基固溶体(溶解有微量的Cu)以及Cu_9Si、MnSi、Mn_6Ni_(16)Si_4等化合物相。     

镍基钎料钎焊不锈钢的钎缝组织及工艺的研究

研究了常用镍基钎料BNi-2钎焊1Cr18Nj9Ti不锈钢的钎缝组织特征和相组成以及采用扩散热处理和加压钎焊工艺对钎缝组织的影响,钎缝宽度对接头性能的影响.研究结果表明,采用合适的扩散热处理和加压钎焊工艺可以有效的消除钎缝组织中的脆性化合物相,合适的钎缝宽度可以提高钎焊接头的物理性能.     

不锈钢真空钎焊接头力学性能分析

对1Cr18Ni9Ti不锈网真空钎焊(采用4种不同钎料)接头的力学性能进行分析。结果表明：钎缝接头的力学性能与其显微组织有关。在本试验条件下，使用BNi-2钎料钎焊，由于钎缝组织出现了大量的化合物相，故其力学性能较差。采用其余3种钎料钎焊时，因钎缝中只有少量的化合物相，其力学性能较好。     

不锈钢真空钎焊接头组织和力学性能研究

采用BNi-2、BNi-5、BDP～1、Cu四种不同钎料真空钎焊1Cr18Ni9Ti不锈钢，对其焊接接头的显微组织和力学性能进行了分析。结果表明：钎缝的组织与钎焊温度和钎料的成分等因素有关。使用BNi-2钎料钎焊得到的钎缝组织中出现了大量的化合物相；而采用BNi-5、BlIP-1钎料，钎缝中有少量化合物相；Cu钎焊时，钎缝中得到单相组织。BNi-2钎焊接头力学性能较差，而其余三种钎料钎焊接头力学性能较好，其中Cu钎焊接头性能最高。     

合金元素Cu对不锈钢钎焊接头组织及性能影响的研究

在BNi-7钎料中添加合金元素Cu用于焊接316L不锈钢,在钎焊温度为980℃、保温时间为10 min、钎焊间隙为100μm的条件下,研究了钎焊接头的微观结构、剪切强度以及端口形貌随不同Cu添加量的变化规律。结果显示,接头主要由不锈钢/钎料界面的Ni(Fe,Cr,Cu)固溶体和钎缝中心大花纹状的Ni(Fe,Cr,Cu)-CrNiP共晶组织和细点状的Ni3P-Ni(Fe,Cr,Cu)共晶组织组成。随着Cu添加量增加,钎缝中心的大花纹状的Ni(Fe,Cr,Cu)-CrNiP共晶组织增加,韧性相Ni(Fe,Cr,Cu)数量增加。接头的抗剪强度随着Cu添加量的增加而增加。当铜添加量为9%时,接头的抗剪强度最大为118 MPa。和不添加合金元素Cu比较,添加Cu元素的接头断口上有较多的撕裂棱,接头的韧性更好。     

真空钎焊不锈钢接头组织及扩散处理研究

采用BNi-2,BNi-5这2种镍基钎料真空钎焊1Cr18Ni9Ti不锈钢.利用金相分析,X射线衍射物相分析方法对钎焊接头组织特性、相组成和扩散处理后组织进行了研究.结果表明:在真空钎焊过程中,钎料和母材中元素产生明显扩散;扩散处理能够消除钎缝中化合物相,使接头组织均匀化.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.